There is a heretofore known imaging device applicable to a digital camera, an optical sensor, and so forth, which mounts an imaging element of CCD type, CMOS type, or other type on an insulating base. As such an imaging device, there is known one comprising: an insulating base having an opening formed at a center thereof and a recess formed at its lower surface, the opening being located inside the recess as seen in a plan view; and an imaging element flip-chip mounted on a bottom surface of the recess of the insulating base (refer to Patent Literature 1, for example). In the insulating base, a connection electrode is placed around the opening of its lower surface, and an external electrode is placed on the outer periphery of the recess. For example, such an imaging device is designed to convert light (image) inputted to a light-receiving section of the imaging element through the opening into an electric signal by the imaging element, and transmit the electric signal to a connection electrode of the insulating base.